1. Field of the Invention
The present invention is directed to a wet clutch arrangement, particularly a wet plate clutch or lockup clutch, comprising a first friction face formation coupled with a housing arrangement for rotation around an axis of rotation and a second friction face formation coupled with an output member for rotation around the axis of rotation, and a preferably ring-shaped pressing piston, wherein the pressing piston and the housing arrangement define a pressure fluid space movable in direction of the axis of rotation through a change in fluid pressure in the pressure fluid space for influencing the frictional interaction between the friction face formations.
2. Description of the Related Art
WO 2007/124720 A1 discloses a hydrodynamic torque converter with a wet clutch arrangement acting as a lockup clutch. This can produce a torque transmission connection between a converter housing and a turbine hub. The wet clutch arrangement comprises, as a first friction face formation, a plurality of plates carried by an outer plate carrier at the converter housing so as to be fixed with respect to relative rotation. The second friction face formation likewise comprises a plurality of plates coupled to the turbine by an inner plate carrier and to the output member by a two-stage torsional vibration damper arrangement.
A ring-shaped pressing piston acts upon the plates in its radial outer area and presses these plates against one another to produce a state of engagement. Somewhat farther inward radially, the pressing piston is guided so as to be movable axially in a fluid-tight manner with respect to the outer plate carrier, which is fixedly supported at the converter housing. In its radial inner end area, the pressing piston is guided to be movable axially in a fluid-tight manner with respect to a ring-shaped hub element secured to the inner side of the converter housing. Accordingly, the pressing piston together with the converter housing defines a pressure fluid space. By supplying pressure fluid to this pressure fluid space, the pressure is increased and a force is generated that acts upon the piston in a direction of the friction face formations. The operant fluid application surface for generating an engaging force corresponds to an annular surface defined between the two radial outer and inner sealing locations of the pressing piston.
For a higher torque to be spontaneously transmitted in a drivetrain with a hydrodynamic torque converter of the type mentioned above, the lockup clutch must be engaged spontaneously, which requires a correspondingly spontaneous increase in the fluid pressure in the pressure fluid space. The existing flow resistance, the volume of the pressure fluid space that must be filled with pressure fluid, and the line resistance in the gearbox all impair the speed at which the lockup clutch is moved into the engaged state. For the driver, this results in unpleasantly noticeable delays in affecting the torque transmission.